The present application teaches a circuit for use in reducing power consumption of a real time clock in a computer system.
When a personal computer is turned off, an on-board battery, e.g. a 3-volt lithium battery, may still power certain circuits in the computer. For example, a real time clock often still maintains the time using battery power when the primary computer power supply goes offline.
The smaller transistors that are now used to make such circuits in order to fit more transistors on a substrate, often have higher leakage currents. These transistors consume undesired current when they are biased to the xe2x80x9coffxe2x80x9d state. This increases the DC load that is placed on the battery, when the computer power supply is off due to off state current, which can cause the battery to deplete more quickly.
The present disclosure defines a device which reduces power consumption during battery powered operation of the Real Time Clock.
The application discloses a leakage reduction device for a real time clock system, that has a real time clock circuit, having separated first and second power supply connections, and maintaining a count indicative of real time; and an associated circuit, which operates in a first mode when a power supply voltage is present and operates in a second mode when battery power is present, said second mode providing a biasing condition that minimizes off state leakage current during battery operation.
These and other aspects will be described in detail with reference to the accompanying drawings, wherein:
FIG. 1 shows a schematic diagram of the circuitry including the real time clock well.
FIG. 2 shows a block diagram of a power monitoring embodiment.